The ROMK potassium channel is present in mammalian urinary tract epithelia and muscle

David A. Spector, Qing Yang, Leonid Klopouh, Jie Deng, Edward J. Weinman, Deborah A. Steplock, Rajatsubhra Biswas, Marc F. Brazie, Jie Liu, James B. Wade

Research output: Contribution to journalArticle

Abstract

There is increasing evidence that mammalian urinary tract epithelial cells utilize membrane channels and transporters to transport solutes across their apical (luminal) and basalateral membranes to modify solute concentrations in both cell and urine. This study investigates the expression, localization, and regulation of the ROMK (Kir 1.1) potassium channels in rat and dog ureter and bladder tissues. Immunoblots of homogenates of whole ureter, whole bladder, bladder epithelial cells, and bladder smooth muscle tissues in both rat and dog identified ∼45- to 50-kDa bands characteristic of ROMK in all tissues. RT-PCR identified ROMK mRNA in these same tissues in both animal species. ROMK protein localized by immunocytochemistry was strongly expressed in the apical membranes of the large umbrella cells lining the bladder lumen and to a lesser extent in the cytoplasm of epithelial cells and smooth muscle cells in the rat bladder. ROMK protein and mRNA were also discovered in cardiac, striated, and smooth muscle in diverse organs. There was no difference in immunoblot expression of ROMK abundance in bladder homogenates (whole bladder, epithelial cell, or muscle cell) or ureteral homogenates between groups of rats fed high- or low-potassium diets. Although the functional role of ROMK in urinary tract epithelia and smooth muscle is unknown, ROMK may participate in the regulation of epithelial and smooth muscle cell volume and osmolality, in the dissipation of potassium leaked or diffused from urine across the epithelial cell apical membranes or tight junctions, and in net or bidirectional potassium transport across urinary tract epithelia.

Original languageEnglish (US)
Pages (from-to)F1658-F1665
JournalAmerican Journal of Physiology - Renal Physiology
Volume295
Issue number6
DOIs
StatePublished - Dec 1 2008

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Keywords

  • Calponin
  • Epithelial sodium channel

ASJC Scopus subject areas

  • Physiology
  • Urology

Cite this

Spector, D. A., Yang, Q., Klopouh, L., Deng, J., Weinman, E. J., Steplock, D. A., Biswas, R., Brazie, M. F., Liu, J., & Wade, J. B. (2008). The ROMK potassium channel is present in mammalian urinary tract epithelia and muscle. American Journal of Physiology - Renal Physiology, 295(6), F1658-F1665. https://doi.org/10.1152/ajprenal.00022.2008